<?php
/**
 * Zend Framework
 *
 * LICENSE
 *
 * This source file is subject to the new BSD license that is bundled
 * with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://framework.zend.com/license/new-bsd
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to license@zend.com so we can send you a copy immediately.
 *
 * @category   Zend
 * @package    Zend_Pdf
 * @copyright  Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 * @version    $Id: Png.php 18993 2009-11-15 17:09:16Z alexander $
 */


/** Internally used classes */
require_once 'Zend/Pdf/Element/Array.php';
require_once 'Zend/Pdf/Element/Dictionary.php';
require_once 'Zend/Pdf/Element/Name.php';
require_once 'Zend/Pdf/Element/Numeric.php';
require_once 'Zend/Pdf/Element/String/Binary.php';


/** Zend_Pdf_Resource_Image */
require_once 'Zend/Pdf/Resource/Image.php';

/**
 * PNG image
 *
 * @package    Zend_Pdf
 * @copyright  Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 */
class Zend_Pdf_Resource_Image_Png extends Zend_Pdf_Resource_Image
{
	const PNG_COMPRESSION_DEFAULT_STRATEGY = 0;
	const PNG_COMPRESSION_FILTERED = 1;
	const PNG_COMPRESSION_HUFFMAN_ONLY = 2;
	const PNG_COMPRESSION_RLE = 3;

	const PNG_FILTER_NONE = 0;
	const PNG_FILTER_SUB = 1;
	const PNG_FILTER_UP = 2;
	const PNG_FILTER_AVERAGE = 3;
	const PNG_FILTER_PAETH = 4;

	const PNG_INTERLACING_DISABLED = 0;
	const PNG_INTERLACING_ENABLED = 1;

	const PNG_CHANNEL_GRAY = 0;
	const PNG_CHANNEL_RGB = 2;
	const PNG_CHANNEL_INDEXED = 3;
	const PNG_CHANNEL_GRAY_ALPHA = 4;
	const PNG_CHANNEL_RGB_ALPHA = 6;

	protected $_width;
	protected $_height;
	protected $_imageProperties;

	/**
	 * Object constructor
	 *
	 * @param string $imageFileName
	 * @throws Zend_Pdf_Exception
	 * @todo Add compression conversions to support compression strategys other than PNG_COMPRESSION_DEFAULT_STRATEGY.
	 * @todo Add pre-compression filtering.
	 * @todo Add interlaced image handling.
	 * @todo Add support for 16-bit images. Requires PDF version bump to 1.5 at least.
	 * @todo Add processing for all PNG chunks defined in the spec. gAMA etc.
	 * @todo Fix tRNS chunk support for Indexed Images to a SMask.
	 */
	public function __construct($imageFileName)
	{
		if (($imageFile = @fopen($imageFileName, 'rb')) === false ) {
			require_once 'Zend/Pdf/Exception.php';
			throw new Zend_Pdf_Exception( "Can not open '$imageFileName' file for reading." );
		}

		parent::__construct();

		//Check if the file is a PNG
		fseek($imageFile, 1, SEEK_CUR); //First signature byte (%)
		if ('PNG' != fread($imageFile, 3)) {
			require_once 'Zend/Pdf/Exception.php';
			throw new Zend_Pdf_Exception('Image is not a PNG');
		}
		fseek($imageFile, 12, SEEK_CUR); //Signature bytes (Includes the IHDR chunk) IHDR processed linerarly because it doesnt contain a variable chunk length
		$wtmp = unpack('Ni',fread($imageFile, 4)); //Unpack a 4-Byte Long
		$width = $wtmp['i'];
		$htmp = unpack('Ni',fread($imageFile, 4));
		$height = $htmp['i'];
		$bits = ord(fread($imageFile, 1)); //Higher than 8 bit depths are only supported in later versions of PDF.
		$color = ord(fread($imageFile, 1));

		$compression = ord(fread($imageFile, 1));
		$prefilter = ord(fread($imageFile,1));

		if (($interlacing = ord(fread($imageFile,1))) != Zend_Pdf_Resource_Image_Png::PNG_INTERLACING_DISABLED) {
			require_once 'Zend/Pdf/Exception.php';
			throw new Zend_Pdf_Exception( "Only non-interlaced images are currently supported." );
		}

		$this->_width = $width;
		$this->_height = $height;
		$this->_imageProperties = array();
		$this->_imageProperties['bitDepth'] = $bits;
		$this->_imageProperties['pngColorType'] = $color;
		$this->_imageProperties['pngFilterType'] = $prefilter;
		$this->_imageProperties['pngCompressionType'] = $compression;
		$this->_imageProperties['pngInterlacingType'] = $interlacing;

		fseek($imageFile, 4, SEEK_CUR); //4 Byte Ending Sequence
		$imageData = '';

		/*
		 * The following loop processes PNG chunks. 4 Byte Longs are packed first give the chunk length
		 * followed by the chunk signature, a four byte code. IDAT and IEND are manditory in any PNG.
		 */
		while(($chunkLengthBytes = fread($imageFile, 4)) !== false) {
			$chunkLengthtmp         = unpack('Ni', $chunkLengthBytes);
			$chunkLength            = $chunkLengthtmp['i'];
			$chunkType                      = fread($imageFile, 4);
			switch($chunkType) {
				case 'IDAT': //Image Data
					/*
					* Reads the actual image data from the PNG file. Since we know at this point that the compression
					* strategy is the default strategy, we also know that this data is Zip compressed. We will either copy
					* the data directly to the PDF and provide the correct FlateDecode predictor, or decompress the data
					* decode the filters and output the data as a raw pixel map.
					*/
					$imageData .= fread($imageFile, $chunkLength);
					fseek($imageFile, 4, SEEK_CUR);
					break;

				case 'PLTE': //Palette
					$paletteData = fread($imageFile, $chunkLength);
					fseek($imageFile, 4, SEEK_CUR);
					break;

				case 'tRNS': //Basic (non-alpha channel) transparency.
					$trnsData = fread($imageFile, $chunkLength);
					switch ($color) {
						case Zend_Pdf_Resource_Image_Png::PNG_CHANNEL_GRAY:
							$baseColor = ord(substr($trnsData, 1, 1));
							$transparencyData = array(new Zend_Pdf_Element_Numeric($baseColor),
							new Zend_Pdf_Element_Numeric($baseColor));
							break;

						case Zend_Pdf_Resource_Image_Png::PNG_CHANNEL_RGB:
							$red = ord(substr($trnsData,1,1));
							$green = ord(substr($trnsData,3,1));
							$blue = ord(substr($trnsData,5,1));
							$transparencyData = array(new Zend_Pdf_Element_Numeric($red),
							new Zend_Pdf_Element_Numeric($red),
							new Zend_Pdf_Element_Numeric($green),
							new Zend_Pdf_Element_Numeric($green),
							new Zend_Pdf_Element_Numeric($blue),
							new Zend_Pdf_Element_Numeric($blue));
							break;

						case Zend_Pdf_Resource_Image_Png::PNG_CHANNEL_INDEXED:
							//Find the first transparent color in the index, we will mask that. (This is a bit of a hack. This should be a SMask and mask all entries values).
							if(($trnsIdx = strpos($trnsData, chr(0))) !== false) {
								$transparencyData = array(new Zend_Pdf_Element_Numeric($trnsIdx),
								new Zend_Pdf_Element_Numeric($trnsIdx));
							}
							break;

						case Zend_Pdf_Resource_Image_Png::PNG_CHANNEL_GRAY_ALPHA:
							// Fall through to the next case

						case Zend_Pdf_Resource_Image_Png::PNG_CHANNEL_RGB_ALPHA:
							require_once 'Zend/Pdf/Exception.php';
							throw new Zend_Pdf_Exception( "tRNS chunk illegal for Alpha Channel Images" );
							break;
					}
					fseek($imageFile, 4, SEEK_CUR); //4 Byte Ending Sequence
					break;

				case 'IEND';
				break 2; //End the loop too

				default:
					fseek($imageFile, $chunkLength + 4, SEEK_CUR); //Skip the section
					break;
			}
		}
		fclose($imageFile);

		$compressed = true;
		$imageDataTmp = '';
		$smaskData = '';
		switch ($color) {
			case Zend_Pdf_Resource_Image_Png::PNG_CHANNEL_RGB:
				$colorSpace = new Zend_Pdf_Element_Name('DeviceRGB');
				break;

			case Zend_Pdf_Resource_Image_Png::PNG_CHANNEL_GRAY:
				$colorSpace = new Zend_Pdf_Element_Name('DeviceGray');
				break;

			case Zend_Pdf_Resource_Image_Png::PNG_CHANNEL_INDEXED:
				if(empty($paletteData)) {
					require_once 'Zend/Pdf/Exception.php';
					throw new Zend_Pdf_Exception( "PNG Corruption: No palette data read for indexed type PNG." );
				}
				$colorSpace = new Zend_Pdf_Element_Array();
				$colorSpace->items[] = new Zend_Pdf_Element_Name('Indexed');
				$colorSpace->items[] = new Zend_Pdf_Element_Name('DeviceRGB');
				$colorSpace->items[] = new Zend_Pdf_Element_Numeric((strlen($paletteData)/3-1));
				$paletteObject = $this->_objectFactory->newObject(new Zend_Pdf_Element_String_Binary($paletteData));
				$colorSpace->items[] = $paletteObject;
				break;

			case Zend_Pdf_Resource_Image_Png::PNG_CHANNEL_GRAY_ALPHA:
				/*
				 * To decode PNG's with alpha data we must create two images from one. One image will contain the Gray data
				 * the other will contain the Gray transparency overlay data. The former will become the object data and the latter
				 * will become the Shadow Mask (SMask).
				 */
				if($bits > 8) {
					require_once 'Zend/Pdf/Exception.php';
					throw new Zend_Pdf_Exception("Alpha PNGs with bit depth > 8 are not yet supported");
				}

				$colorSpace = new Zend_Pdf_Element_Name('DeviceGray');

				require_once 'Zend/Pdf/ElementFactory.php';
				$decodingObjFactory = Zend_Pdf_ElementFactory::createFactory(1);
				$decodingStream = $decodingObjFactory->newStreamObject($imageData);
				$decodingStream->dictionary->Filter      = new Zend_Pdf_Element_Name('FlateDecode');
				$decodingStream->dictionary->DecodeParms = new Zend_Pdf_Element_Dictionary();
				$decodingStream->dictionary->DecodeParms->Predictor        = new Zend_Pdf_Element_Numeric(15);
				$decodingStream->dictionary->DecodeParms->Columns          = new Zend_Pdf_Element_Numeric($width);
				$decodingStream->dictionary->DecodeParms->Colors           = new Zend_Pdf_Element_Numeric(2);   //GreyAlpha
				$decodingStream->dictionary->DecodeParms->BitsPerComponent = new Zend_Pdf_Element_Numeric($bits);
				$decodingStream->skipFilters();

				$pngDataRawDecoded = $decodingStream->value;

				//Iterate every pixel and copy out gray data and alpha channel (this will be slow)
				for($pixel = 0, $pixelcount = ($width * $height); $pixel < $pixelcount; $pixel++) {
					$imageDataTmp .= $pngDataRawDecoded[($pixel*2)];
					$smaskData .= $pngDataRawDecoded[($pixel*2)+1];
				}
				$compressed = false;
				$imageData  = $imageDataTmp; //Overwrite image data with the gray channel without alpha
				break;

			case Zend_Pdf_Resource_Image_Png::PNG_CHANNEL_RGB_ALPHA:
				/*
				 * To decode PNG's with alpha data we must create two images from one. One image will contain the RGB data
				 * the other will contain the Gray transparency overlay data. The former will become the object data and the latter
				 * will become the Shadow Mask (SMask).
				 */
				if($bits > 8) {
					require_once 'Zend/Pdf/Exception.php';
					throw new Zend_Pdf_Exception("Alpha PNGs with bit depth > 8 are not yet supported");
				}

				$colorSpace = new Zend_Pdf_Element_Name('DeviceRGB');

				require_once 'Zend/Pdf/ElementFactory.php';
				$decodingObjFactory = Zend_Pdf_ElementFactory::createFactory(1);
				$decodingStream = $decodingObjFactory->newStreamObject($imageData);
				$decodingStream->dictionary->Filter      = new Zend_Pdf_Element_Name('FlateDecode');
				$decodingStream->dictionary->DecodeParms = new Zend_Pdf_Element_Dictionary();
				$decodingStream->dictionary->DecodeParms->Predictor        = new Zend_Pdf_Element_Numeric(15);
				$decodingStream->dictionary->DecodeParms->Columns          = new Zend_Pdf_Element_Numeric($width);
				$decodingStream->dictionary->DecodeParms->Colors           = new Zend_Pdf_Element_Numeric(4);   //RGBA
				$decodingStream->dictionary->DecodeParms->BitsPerComponent = new Zend_Pdf_Element_Numeric($bits);
				$decodingStream->skipFilters();

				$pngDataRawDecoded = $decodingStream->value;

				//Iterate every pixel and copy out rgb data and alpha channel (this will be slow)
				for($pixel = 0, $pixelcount = ($width * $height); $pixel < $pixelcount; $pixel++) {
					$imageDataTmp .= $pngDataRawDecoded[($pixel*4)+0] . $pngDataRawDecoded[($pixel*4)+1] . $pngDataRawDecoded[($pixel*4)+2];
					$smaskData .= $pngDataRawDecoded[($pixel*4)+3];
				}

				$compressed = false;
				$imageData  = $imageDataTmp; //Overwrite image data with the RGB channel without alpha
				break;

			default:
				require_once 'Zend/Pdf/Exception.php';
				throw new Zend_Pdf_Exception( "PNG Corruption: Invalid color space." );
		}

		if(empty($imageData)) {
			require_once 'Zend/Pdf/Exception.php';
			throw new Zend_Pdf_Exception( "Corrupt PNG Image. Mandatory IDAT chunk not found." );
		}

		$imageDictionary = $this->_resource->dictionary;
		if(!empty($smaskData)) {
			/*
			 * Includes the Alpha transparency data as a Gray Image, then assigns the image as the Shadow Mask for the main image data.
			 */
			$smaskStream = $this->_objectFactory->newStreamObject($smaskData);
			$smaskStream->dictionary->Type             = new Zend_Pdf_Element_Name('XObject');
			$smaskStream->dictionary->Subtype          = new Zend_Pdf_Element_Name('Image');
			$smaskStream->dictionary->Width            = new Zend_Pdf_Element_Numeric($width);
			$smaskStream->dictionary->Height           = new Zend_Pdf_Element_Numeric($height);
			$smaskStream->dictionary->ColorSpace       = new Zend_Pdf_Element_Name('DeviceGray');
			$smaskStream->dictionary->BitsPerComponent = new Zend_Pdf_Element_Numeric($bits);
			$imageDictionary->SMask = $smaskStream;

			// Encode stream with FlateDecode filter
			$smaskStreamDecodeParms = array();
			$smaskStreamDecodeParms['Predictor']        = new Zend_Pdf_Element_Numeric(15);
			$smaskStreamDecodeParms['Columns']          = new Zend_Pdf_Element_Numeric($width);
			$smaskStreamDecodeParms['Colors']           = new Zend_Pdf_Element_Numeric(1);
			$smaskStreamDecodeParms['BitsPerComponent'] = new Zend_Pdf_Element_Numeric(8);
			$smaskStream->dictionary->DecodeParms  = new Zend_Pdf_Element_Dictionary($smaskStreamDecodeParms);
			$smaskStream->dictionary->Filter       = new Zend_Pdf_Element_Name('FlateDecode');
		}

		if(!empty($transparencyData)) {
			//This is experimental and not properly tested.
			$imageDictionary->Mask = new Zend_Pdf_Element_Array($transparencyData);
		}

		$imageDictionary->Width            = new Zend_Pdf_Element_Numeric($width);
		$imageDictionary->Height           = new Zend_Pdf_Element_Numeric($height);
		$imageDictionary->ColorSpace       = $colorSpace;
		$imageDictionary->BitsPerComponent = new Zend_Pdf_Element_Numeric($bits);
		$imageDictionary->Filter       = new Zend_Pdf_Element_Name('FlateDecode');

		$decodeParms = array();
		$decodeParms['Predictor']        = new Zend_Pdf_Element_Numeric(15); // Optimal prediction
		$decodeParms['Columns']          = new Zend_Pdf_Element_Numeric($width);
		$decodeParms['Colors']           = new Zend_Pdf_Element_Numeric((($color==Zend_Pdf_Resource_Image_Png::PNG_CHANNEL_RGB || $color==Zend_Pdf_Resource_Image_Png::PNG_CHANNEL_RGB_ALPHA)?(3):(1)));
		$decodeParms['BitsPerComponent'] = new Zend_Pdf_Element_Numeric($bits);
		$imageDictionary->DecodeParms  = new Zend_Pdf_Element_Dictionary($decodeParms);

		//Include only the image IDAT section data.
		$this->_resource->value = $imageData;

		//Skip double compression
		if ($compressed) {
			$this->_resource->skipFilters();
		}
	}

	/**
	 * Image width
	 */
	public function getPixelWidth() {
		return $this->_width;
	}

	/**
	 * Image height
	 */
	public function getPixelHeight() {
		return $this->_height;
	}

	/**
	 * Image properties
	 */
	public function getProperties() {
		return $this->_imageProperties;
	}
}
